JP5390631B2 - Nonvolatile memory element and manufacturing method thereof - Google Patents

Description

  The present invention relates to a nonvolatile memory element and a method for manufacturing the same, and more particularly to a variable resistance nonvolatile memory element and a method for manufacturing the same.

  A flash memory using a floating gate, which is currently mainstream, has a problem that a threshold voltage (Vth) fluctuation occurs due to interference due to capacitive coupling between floating gates of adjacent cells as the memory cell becomes finer. . Therefore, as a memory having a structure suitable for miniaturization, development of a resistance change type nonvolatile memory element in which a layer causing resistance change is sandwiched between electrodes is underway. This variable resistance nonvolatile element is characterized in that the electric resistance of the resistance layer can be switched to two or more values by electrical stimulation, and miniaturization and cost reduction are possible due to the simplicity of the element structure and operation. It is expected as a non-volatile element that is possible.

As a layer whose resistance is changed by an applied voltage (resistance change layer), there is an oxide of an element selected from a group formed from a transition metal, such as nickel oxide (NiO), vanadium oxide (V ₂ O). ₅ ), zinc oxide (ZnO), niobium oxide (Nb ₂ O ₅ ), titanium oxide (TiO ₂ ), tungsten oxide (WO ₃ ), cobalt oxide (CoO), tantalum oxide (Ta ₂ O) ₅ ). The variable resistance layer includes a metal oxide having a composition deviating from a stoichiometric composition made of Ni, Ti, Ta, Hf, Nb, Zn, W, Co, or the like.

  The operating principle of resistance change is unknown, but when a voltage is applied to the resistance change layer, a current path called a filament is formed in the resistance change layer. The principle that the resistance changes and the principle that the resistance of the resistance change layer changes due to the movement of oxygen atoms at the interface between the electrode and the resistance change layer have been reported.

  FIG. 12 is a schematic diagram showing a cross-sectional structure of a conventional variable resistance nonvolatile memory element (ReRAM: Resistive Random Access Memory) with reference to Patent Document 1. A general ReRAM resistance change element (memory element) 610 includes a resistance change film (for example, a transition metal oxide film) 613 sandwiched between a lower electrode 612 and an upper electrode 614 formed on an interlayer insulating film 611. It has a parallel plate type laminated structure. When a voltage is applied between the upper electrode 614 and the lower electrode 612, the electric resistance of the resistance change film 613 is changed to take two different resistance states (reset state and set state). Note that Patent Document 2 describes that the upper electrode 614 is made of Pt, and the lower electrode 612 is made of a material containing at least one element selected from Ru, Ti, Al, Ta, Cu, W, and Ni. Yes.

  The operation mechanism of the resistance change element 610 first applies a forming voltage as an initial operation for enabling an electrical transition between two resistance states. By applying the forming voltage, the variable resistance film 613 is in a state in which a filament serving as a current path can be formed. Thereafter, the generation state of the filament is changed by application of operating voltages (set voltage and reset voltage), and set / reset operations, that is, writing and erasing are executed. The larger the area of the variable resistance element 610, the greater the number of filaments. However, as the number of filaments increases, the reset current control varies, and as a result, the operation as a memory varies. In order to realize a stable and reliable operation as well as a demand for higher density, it is desirable that the operating area of the resistance change element 610 be smaller. However, as described above, in the conventional structure, miniaturization is limited by the processing accuracy of the photolithography technique.

  Non-Patent Document 1 proposes a nonvolatile memory device in which Pt is used as the upper and lower electrodes and the resistance change layer is made of NiO. A current path called a filament is formed in the Ni oxide, and the resistance is changed. Is said to change. Non-Patent Document 2 proposes a nonvolatile memory device in which Pt is used as the upper and lower electrodes and the resistance change layer is made of TaOx, and the resistance changes due to the movement of oxygen atoms in the interface layer between the Pt electrode and TaOx. It is stated.

  Further, a technique relating to a resistance change element using a titanium nitride electrode that can be easily etched as an electrode material has attracted attention. Non-Patent Document 3 proposes a non-volatile memory device using Pt as the lower electrode, HfOx or HfAlOx as the resistance change layer, and TiN as the upper electrode, and operates by using HfAlOx as the resistance change layer. It is stated that voltage variations can be suppressed. Further, Non-Patent Document 4 states that a resistance change operation can be realized by forming a TiN / Ti / HfO2 / TiN laminated structure of TiN / TiOx / HfOx / TiN by oxygen annealing. .

JP 2009-141275 A Japanese Patent No. 3919205

APPLYEDPHYSICS LETTERS 86,093509 (2005) Internationalelectron devices meeting technical digest, 2008, P293-P296 Symposium VLSI technology digiest of technical papers, 2009. p30-P31 Internationalelectron devices meeting technical digest, 2008, P297-P300

  However, each of the above-described techniques has the following problems. First, the technique of using a Pt electrode as an electrode of a resistance change element as in Non-Patent Document 1 is effective in suppressing the operational instability of element characteristics due to the oxidation of the electrode, but etching in the electrode processing process is effective. There is a problem that it is difficult and it is difficult to reduce material costs. Secondly, in the method described in Non-Patent Document 4, the technique of using a TiN electrode as an electrode material is effective in reducing etching ease and material cost. However, there is a concern about deterioration of device characteristics due to oxidation of TiN. Moreover, there is a problem that nothing is described regarding the range of the optimum form of the TiN electrode. Thirdly, as described in Patent Document 2, the technique using Pt as the upper electrode material and Ti as the lower electrode material makes it difficult to use the Pt electrode constituting the upper electrode, and the oxidation of the lower electrode material. There is a problem that there is a concern about deterioration of element characteristics due to the above.

  The present invention has been made with respect to the above-described conventional problems. The object of the present invention is to reduce the occurrence of deterioration of the electrical characteristics of the element in the nonvolatile semiconductor device having the variable resistance layer, and to process the electrode. An object of the present invention is to provide a nonvolatile memory element that can be easily manufactured at low cost, and a method for manufacturing the same.

  The configuration of the present invention made to achieve the above object is as follows.

  That is, the present invention relates to a variable resistor that changes its resistance value between two different resistance states sandwiched between the first electrode, the second electrode, and the first electrode and the second electrode. In the nonvolatile memory element including the layer, at least one of the first electrode and the second electrode is an electrode including a metal nitride layer containing at least Ti and N, and the metal From the metal nitride layer in which the molar ratio (N / Ti ratio) of Ti and N in the nitride layer at least in the portion in contact with the variable resistance layer is 1.15 or more and the film density is 4.7 g / cc or more It is characterized by becoming.

  In addition, the present invention provides a variable resistor that changes its resistance value between two different resistance states sandwiched between the first electrode, the second electrode, and the first electrode and the second electrode. A method of manufacturing a nonvolatile memory element including a layer, wherein at least one of the first electrode and the second electrode is an electrode including a metal nitride layer containing at least Ti and N The molar ratio of Ti and N (N / Ti ratio) of at least a portion in contact with the variable resistance layer of the metal nitride layer is 1.1 or more, and the film density is 4.7 g / cc or more. And a step of forming a metal nitride layer having a crystal orientation X in the range of 1.2 <X.

  According to the present invention, an electrode suitable for a resistance variable nonvolatile semiconductor element can be realized by controlling the film composition, film density, and crystal orientation of TiN.

It is a figure which shows the cross section of the element structure which concerns on embodiment of this invention. It is a figure which shows the outline of the processing apparatus used for the formation process of the titanium nitride film which concerns on embodiment of this invention. It is a figure which shows the film composition of the titanium nitride film concerning embodiment of this invention, the film density, and the relationship of an effective work function. It is a figure which shows the XRD diffraction spectrum of the titanium nitride film which concerns on embodiment of this invention. It is a figure which shows the relationship of the peak intensity ratio and film | membrane composition in the XRD diffraction spectrum of the titanium nitride film which concerns on embodiment of this invention. It is a figure which shows the observation image by SEM of the titanium nitride film which concerns on embodiment of this invention. It is a figure which shows the cross-section of the element based on Example 1 of this invention. It is a figure which shows the current-voltage characteristic of the element which concerns on Example 1 of this invention. It is a figure which shows the endurance characteristic of the element which concerns on Example 1 of this invention. It is a schematic diagram of the control apparatus 400 which controls the processing apparatus of FIG. It is the figure which showed the internal structure of the control mechanism 400 of FIG. It is the schematic which shows the cross-section of the conventional variable resistance non-volatile memory element (ReRAM: Resistive Random Access Memory).

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  In the variable resistance nonvolatile semiconductor device having a variable resistance layer and an electrode made of a metal nitride layer containing Ti and N as first and second electrodes, titanium nitride suitable for resistance change As a result of diligent examination of the film structure, the molar ratio of Ti and N (N / Ti ratio) of at least the portion in contact with the variable resistance layer of the metal nitride layer is 1.15 or more, and the film density is 4.7 g / cc. It has been found that a variable resistance nonvolatile semiconductor device having a high resistance change ratio can be realized by applying a titanium nitride film that has the above-described crystal orientation X in a range of 1.1 <X. . Here, in the present invention, “crystal orientation” means the ratio of (200) peak intensity to (111) peak intensity in the X-ray diffraction spectrum of a metal nitride layer containing Ti and N (C (200) / C (111)).

  The form of the titanium nitride film suitable for the variable resistance element according to one embodiment of the present invention will be described using the variable resistance element of FIG. 1 as an example. As shown in FIG. 1, a titanium nitride film 2 as a first electrode is formed on a base substrate 1 having a silicon oxide film on the surface, a variable resistance layer 3 is formed on the titanium nitride film 2, and a first layer is formed on the variable resistance layer 3. A titanium nitride film 4 as the second electrode is formed.

  FIG. 2 shows an outline of a processing apparatus used in the process of forming a titanium nitride film constituting the first electrode in one embodiment of the present invention.

  The film forming chamber 100 can be heated to a predetermined temperature by a heater 101. The substrate 102 to be processed can be heated to a predetermined temperature by a heater 105 via a susceptor 104 incorporated in a substrate support base 103. It is preferable that the substrate support 103 can be rotated at a predetermined rotational speed from the viewpoint of film thickness uniformity. In the film formation chamber, a target 106 is installed at a position where the target substrate 102 is desired. The target 106 is installed on the target holder 108 via a back plate 107 made of a metal such as Cu. It should be noted that the outer shape of the target assembly in which the target 106 and the back plate 107 are combined may be made of a target material as a single component and attached as a target. That is, a configuration in which the target is installed on the target holder may be used. A direct current power source 110 for applying power for sputtering discharge is connected to the target holder 108 made of metal such as Cu, and is insulated from the wall of the film formation processing chamber 100 at the ground potential by an insulator 109. A magnet 111 for realizing magnetron sputtering is disposed behind the target 106 as viewed from the sputtering surface. The magnet 111 is held by a magnet holder 112 and can be rotated by a magnet holder rotation mechanism (not shown). In order to make the erosion of the target uniform, the magnet 111 rotates during discharge. The target 106 is installed at an offset position obliquely above the substrate 102. That is, the center point of the sputtering surface of the target 106 is at a position that is shifted by a predetermined dimension with respect to the normal line of the center point of the substrate 102. A shielding plate 116 is disposed between the target 106 and the processing substrate 102 to control film formation on the processing substrate 102 by sputtered particles emitted from the target 106 to which power is supplied.

  As the target, for example, a Ti metal target 106 can be used. The deposition of the titanium nitride film is performed by supplying electric power to the metal target 106 from the DC power source 110 via the target holder 108 and the back plate 107, respectively. At this time, an inert gas is introduced into the processing chamber 100 from the vicinity of the target from the inert gas source 201 through the valve 202, the mass flow controller 203, and the valve 204. A reactive gas composed of nitrogen is introduced from the nitrogen gas source 205 to the vicinity of the substrate in the processing chamber 100 through the valve 206, the mass flow controller 207, and the valve 208. The introduced inert gas and reactive gas are exhausted by the exhaust pump 118 via the conductance valve 117.

  Titanium nitride deposition in one embodiment of the present invention uses argon as the sputtering gas and nitrogen as the reactive gas. The substrate temperature is 27 ° C. to 600 ° C., the target power is 50 W to 1000 W, the sputtering gas pressure is 0.2 Pa to 1.0 Pa, the Ar flow rate is 0 sccm (standard cc / min) to 100 sccm, the nitrogen gas flow rate is 0 sccm to 100 sccm, It can be determined as appropriate within the range. Here, deposition was performed at a substrate temperature of 30 ° C., a Ti target power of 750 W, a sputtering gas pressure of 0.2 Pa, an argon gas flow rate of 0 sccm to 20 sccm, and a nitrogen gas flow rate of 2 sccm to 50 sccm. The molar ratio of Ti element and N element in the titanium nitride film and the crystal orientation can be adjusted by the mixing ratio of argon and nitrogen introduced during sputtering. In the present specification, the “molar ratio” refers to the ratio of the number of moles, which is the basic unit of the substance amount. The molar ratio between the Ti element and the N element can be measured, for example, from X-ray photoelectron spectroscopy based on the binding energy of electrons inherent in the substance, the energy level of electrons, and the electron intensity distribution.

Next, the variable resistance layer 3 is formed by a film forming apparatus similar to the film forming apparatus used in the step of forming the first electrode 2. Examples of the material used for the variable resistance layer 3 include oxides containing one or more elements selected from the group formed of transition metals, such as nickel oxide (NiO), vanadium oxide ( V ₂ O ₅ ), zinc oxide (ZnO), niobium oxide (Nb ₂ O ₅ ), titanium oxide (TiO ₂ ), tungsten oxide (WO ₃ ), cobalt oxide (CoO), tantalum oxide ( Ta ₂ O ₅ ). Examples of the material used for the variable resistance layer 3 include metal oxides having a composition deviating from the stoichiometric composition composed of Ni, Ti, Ta, Hf, Nb, Zn, W, Co, and the like. . Moreover, the metal oxide containing Hf and Al is mentioned. Here, a metal layer containing Hf and Al was deposited using an Hf metal target and an Al metal target.

  Next, the deposited metal film containing Hf and Al is annealed in an oxygen atmosphere in the range of 300 ° C. to 600 ° C. to form a variable resistance layer made of a metal oxide. The annealing treatment in an oxygen atmosphere is preferably 300 ° C. or higher in order to oxidize the metal film. Further, the temperature is preferably 600 ° C. or lower in order to suppress deterioration of device characteristics due to oxidation of the titanium nitride film constituting the first electrode. In the annealing process at 600 ° C. or higher, the titanium nitride film is oxidized and resistance change does not occur.

  Next, a titanium nitride film is deposited as the second electrode 4 by the same method as in the step of forming the first electrode 2.

  Next, the TiN film is processed into a desired size using a lithography technique and an RIE (Reactive Ion Etching) technique to form an element. The composition of the deposited titanium nitride film was analyzed by an X-ray photoelectron spectroscopy (XPS) method. In addition, the crystal orientation of the titanium nitride film was analyzed by an X-ray diffraction (XRD: X-ray Diffraction) method. The film density was analyzed by the X-ray reflectometer method. Moreover, the resistance change characteristic of the produced element was evaluated by IV measurement.

  FIG. 3 shows a film composition of nitrogen N and titanium Ti of the titanium nitride film (N / Ti ratio: corresponding to ● in the figure) and a film composition of oxygen O and titanium Ti of the titanium nitride film in one embodiment of the present invention ( (O / Ti ratio: corresponding to □ in the figure) and the film density. As a result of evaluating the switching characteristics of the variable resistance element manufactured in the present embodiment, the resistance in a region where the film density shown in the figure is 4.7 g / cc or more and the film composition N / Ti ratio is 1.15 or more. It was confirmed that switching operation by change was obtained. On the other hand, in the region where the film density is smaller than 4.7 g / cc and the film composition N / Ti ratio is smaller than 1.15, the switching operation due to the resistance change cannot be obtained. This is considered to be because the film composition O / Ti ratio shown in FIG. 3 increases in the region where the film density is smaller than 4.7 g / cc and the film composition N / Ti ratio is small. . That is, it is suggested that when the oxygen in the variable resistance change layer moves into the titanium nitride film to some extent, the resistance change due to voltage application does not occur.

  Next, condition A (argon gas flow rate 10 sccm, nitrogen gas flow rate 10 sccm), condition B (argon gas flow rate 0 sccm, nitrogen gas flow rate 50 sccm) and condition C (argon gas flow rate 13.5 sccm, nitrogen gas flow rate) shown in FIG. FIG. 4 shows an XRD spectrum of the titanium nitride film deposited at 6 sccm). C (111), C (200), and C (220) in FIG. 4 represent the crystal plane, (111) plane, (200) plane, and (220) plane of the titanium nitride film, respectively. As shown in the figure, the titanium nitride film capable of changing the resistance in one embodiment of the present invention has a crystal structure with high crystal orientation on the (200) plane.

  FIG. 5 shows the film composition (N / Ti ratio) of the titanium nitride film in one embodiment of the present invention, and the peak intensity ratio C (200) / (111) face and (200) face in the XRD spectrum shown in FIG. The relationship with C (111) is shown. As shown in FIG. 5, the titanium nitride film having a film composition N / Ti ratio of 1.15 or more with which resistance change operation can be obtained in one embodiment of the present invention has a peak intensity ratio (crystal orientation) of 1.2. It has the above. Here, the morphology of the titanium nitride film having a peak intensity ratio (crystal orientation) as high as 1.2 or higher was evaluated by cross-section and surface observation by SEM (scanning electron microscope). FIG. 6 shows a SEM observation image of the titanium nitride film deposited under the condition A. As shown in FIG. 6, it can be confirmed that the titanium nitride film in one embodiment of the present invention has a columnar structure with a grain size of 20 nm or less and is excellent in surface flatness. This small grain size and excellent surface flatness are considered to suppress the leakage current caused by the crystal grain boundary and obtain a high resistance change ratio necessary for the resistance change element. Further, it is considered that the fact that the grain size is small and the crystal structure is dense leads to the improvement of the film density.

  From the above results, in the titanium nitride film in one embodiment of the present invention, the molar ratio of Ti and N in the titanium nitride film is preferably 1.15 or more in order to obtain a resistance change operation, and the film density is 4 0.7 g / cc or more is preferable. The C (220) / C (111) peak intensity ratio X in the XRD spectrum representing the crystal orientation of the metal nitride layer is preferably 1.2 or more.

  Further, the titanium nitride film deposition step in one embodiment of the present invention is shown in FIG. 2 in order to suppress deterioration of device characteristics due to plasma damage to the variable resistance layer 3 and to control composition and crystal orientation. In the vacuum vessel 100 in which the target 106 is installed at an offset position obliquely above the substrate 102, the Ti target 106 is placed in a mixed atmosphere of a reactive gas composed of nitrogen and an inert gas (for example, argon). A step of performing magnetron sputtering, in which the molar ratio of Ti and N in the metal nitride layer is 1.15 or more, and the nitrogen gas and the inert gas are mixed so that the crystal orientation X1 satisfies the range of 1.2 <X. It is preferable to set the mixing ratio.

  In the above description, the element containing Hf and Al is described as the variable resistance layer 3, but the present invention is not limited to this, and the effect of the present invention is Ni, Ti, Ta, Hf as the variable resistance layer 3. , Zr, V, Zn, Nb, W, or a metal oxide containing at least one of Co can also be used.

  In addition, as a step of forming the variable resistance layer 3, an Al target 106 is used as the Hf target 106 to form a laminated film including a metal film of Hf and Al, and then an annealing process is performed at 300 ° C. to 600 ° C. in an oxygen atmosphere. You may use the method to do.

  Further, as a step of forming the variable resistance layer 3, after depositing a metal film containing Hf and Al using co-sputtering of the Hf target 106 and the Al target 106, an annealing process at 300 ° C. to 600 ° C. is performed in an oxygen atmosphere. The method of implementation may be used.

  Further, as the step of forming the variable resistance layer 3, a step of performing magnetron sputtering of the Hf target 106 and the Al target 106 in a mixed atmosphere of a reactive gas composed of oxygen and an inert gas may be used.

  Further, as a step of forming the variable resistance layer 3, after depositing a metal film selected from at least one of Ni, Ti, Ta, Hf, Zr, V, Zn, Nb, W or Co and a laminated film thereof, oxygen An annealing treatment at 300 ° C. to 600 ° C. may be performed in an atmosphere.

  Further, as a step of forming the variable resistance layer 3, a metal target selected from at least one of Ni, Ti, Ta, Hf, Zr, V, Zn, Nb, W, or Co is used as a reactive gas composed of oxygen and inert. A step of performing magnetron sputtering in a mixed gas atmosphere may be used.

  In the above description, the structure of the variable resistance element having the titanium nitride film as the first electrode and the second electrode has been described. However, the present invention is not limited to this, and the present invention is applied to at least one of the electrodes. If the titanium nitride film satisfying the above condition is included, the effect can be sufficiently obtained. In that case, as one of the electrodes, an electrode containing any one of Pt, Ru, W, and Ir can be selected.

  Next, a control device 400 for controlling the processing apparatus shown in FIG. 2 used in the process of forming a titanium nitride film that is a material of the first electrode 2 or the second electrode 4 of the present embodiment will be described. FIG. 10 is a schematic diagram of a control device 400 that controls the processing device shown in FIG. The valves 202, 204, 206, and 208 can be controlled to open and close by the control device 400 via the control input / output ports 500, 501, 502, and 503, respectively. The mass flow controllers 203 and 207 can adjust the flow rate by the control device 400 via the control input / output ports 504 and 505, respectively. Further, the opening of the conductance valve 117 can be adjusted by the control device 400 via the control input / output port 506. Further, the temperature of the heater 105 can be adjusted by the control device 400 via the input / output port 507. Further, the rotation state of the substrate support 103 can be adjusted by the control device 400 via the input / output port 508. Further, the frequency and supply power of the DC power source 110 can be adjusted by the control device 400 via the input / output port 509.

  In one embodiment of the present invention, the control mechanism 400 causes the molar ratio of Ti and N (N / Ti ratio) of the metal nitride layer at least in contact with the variable resistance layer 3 to be 1.15 or more, and the film The mixing ratio of argon gas and nitrogen gas introduced at the time of sputtering film formation is controlled so that the density becomes 4.7 g / cc or more.

  FIG. 11 is a diagram illustrating an internal configuration of the control mechanism 400. The control mechanism 400 includes an input unit 401, a storage unit 402 having a program and data, a processor 403, and an output unit 404. The control mechanism 400 basically has a computer configuration and controls the processing apparatus shown in FIG.

  Further, in the storage unit 402, a variable resistance layer is provided between the first electrode and the second electrode, and a program for giving a command for controlling the formation process of the first electrode and the second electrode to the computer. And a program for issuing a command for controlling the forming process.

  Note that a specific program in the storage unit 402 is that, as the first electrode, the molar ratio of Ti and N (N / Ti ratio) is 1.15 or more and the film density is 4.7 g / cc or more. And a step of forming a metal nitride layer having a crystal orientation X in the range of 1.2 <X, a step of forming a metal film containing Hf and Al, and the metal film at 300 ° C. or more and 600 ° C. A step of forming a variable resistance layer made of a metal oxide by heat treatment in the following oxygen atmosphere, and, as the second electrode, a molar ratio of Ti and N (N / Ti ratio) is 1.15 or more, and And a step of forming a metal nitride layer having a film density of 4.7 g / cc or more and a crystal orientation X in a range of 1.2 <X.

  A first embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 7 is a schematic cross-sectional view of the element structure according to the first embodiment. A silicon substrate 11 having a silicon oxide film with a thickness of 100 nm on the surface thereof has a molar ratio of Ti and N of 1. with an argon gas flow rate of 10 sccm and a nitrogen gas flow rate of 10 sccm using a Ti metal target in the processing apparatus shown in FIG. A titanium nitride film 12 having a thickness of 15 or more and a crystal orientation X1 in the range of 1.2 <X was deposited to 20 nm. Thereafter, annealing at 500 ° C. for 10 min in a nitrogen atmosphere and annealing at 500 ° C. for 30 min in an oxygen atmosphere were performed to form the variable resistance layer 13 made of a metal oxide containing Hf and Al.

  Next, a titanium nitride film 14 was deposited on the variable resistance layer 13 by the same method as the titanium nitride film 12. Next, the TiN film was processed into a desired size using a lithography technique and an RIE (Reactive Ion Etching) technique.

  The composition of the deposited titanium nitride film was analyzed by an X-ray photoelectron spectroscopy (XPS) method. In addition, the crystal orientation of the titanium nitride film was analyzed by an X-ray diffraction (XRD: X-ray Diffraction) method. The film density was analyzed by the X-ray reflectometer method. Further, the resistance changing operation of the manufactured element was evaluated by IV measurement.

  FIG. 8 shows IV characteristics of the manufactured variable resistance element. The IV characteristics are as follows: the titanium nitride film 12 of the device is grounded, and the titanium nitride film 14 has 0V → −2V (corresponding to the data of ○ in the figure) and −2V → 0V (indicated by the data of Δ in the figure). Corresponding), 0V → 2.5V (corresponding to the data of □ in the figure), 2.5V → 0V (corresponding to the diamond data in the figure) were applied and measured. As shown in FIG. 8, when a voltage is applied to the titanium nitride film 14 in the range of 0V → −2V, the state changes from the high resistance state to the low resistance state (Set operation) at V = −1.9V (set state). ) Increase in current value can be confirmed. Next, when a voltage is applied to the titanium nitride film 14 in the range of 0V → 2.5V, the current value decreases due to the state (reset operation) that changes from the low resistance state to the high resistance state at V = 2.2V (Reset operation). Can be confirmed. Thus, in the variable resistance element having the titanium nitride film of one embodiment of the present invention, it is shown that a variable resistance element having an On / 0ff ratio of 103 or more in the low resistance state and the high resistance state can be formed.

  In FIG. 9, positive and negative pulses (+3 V applied for 0.1 sec, −2.5 V applied for 0.1 sec, see FIG. 9) are alternately and continuously applied to the manufactured variable resistance element. The result of evaluating durability (endurance characteristics) is shown. FIG. 9 shows measurement results up to 200 times of pulse application. As shown in the figure, the high resistance state and the low resistance state change corresponding to the applied pulse, and even when 200 pulses are applied, the value in the high resistance state (1 MΩ) and the value in the low resistance state (300Ω) Can be confirmed. As described above, in the variable resistance element having the titanium nitride film according to the embodiment of the present invention, a change in resistance value due to deterioration of the element could not be confirmed even in continuous operation by a pulse. Note that FIG. 9 does not mean that the resistance change phenomenon is not observed after 200 pulses are applied, and the element showed a stable resistance change after this.

  In the above-described embodiment, the case where the Hf and Al metal laminated film is used as the method of forming the variable resistance layer 3 is described. However, the co-sputtering of the Hf target 106 and the Al target 106 is used as the variable resistance layer 3 forming step. After depositing a metal film containing Hf and Al, it was confirmed that the same effect as in the above example could be obtained even by using a method of annealing at 300 ° C. to 600 ° C. in an oxygen atmosphere. Further, the same effect as in the above embodiment can be obtained by using a step of magnetron sputtering the Hf target 106 and the Al target 106 in a mixed atmosphere of a reactive gas and an inert gas made of oxygen. It was confirmed that it was obtained.

  In the above embodiment, the case where a metal oxide containing Hf and Al is used as the material of the variable resistance layer 3 is described. However, Ni, Ti, Ta, Hf, Zr, V, Zn, Nb are used as the variable resistance layer 3. It was confirmed that even when a metal oxide film selected from at least one of W, Co, and a laminated film thereof was used, the same effect as in the above example was obtained.

  Further, as a step of forming the variable resistance layer 3, after depositing a metal film selected from at least one of Ni, Ti, Ta, Hf, Zr, V, Zn, Nb, W or Co and a laminated film thereof, an oxygen atmosphere It was confirmed that a resistance change element capable of obtaining the same effect can be formed even when annealing at 300 ° C. to 600 ° C. is performed. In addition, as a step of forming the variable resistance layer 3, a metal target selected from at least one of Ni, Ti, Ta, Hf, Zr, V, Zn, Nb, W, or Co is used as a reactive gas composed of oxygen and an inert gas. It was confirmed that the same effect as in the above example could be obtained even using the magnetron sputtering step in the mixed atmosphere.

Claims (18)

A first electrode;
A second electrode;
In a nonvolatile memory element including a variable resistance layer having a resistance value that changes between two different resistance states sandwiched between the first electrode and the second electrode.
At least one of the first electrode and the second electrode is an electrode including a metal nitride layer containing at least Ti and N;
The molar ratio of Ti and N (N / Ti ratio) of at least a portion in contact with the variable resistance layer of the metal nitride layer is 1.15 or more, and the film density is 4.7 g / cc or more. A nonvolatile memory element.   The nonvolatile memory element according to claim 1, wherein crystal orientation X of at least a portion of the metal nitride layer in contact with the variable resistance layer has a range of 1.2 <X.   The nonvolatile memory according to claim 1, wherein the variable resistance layer includes a metal oxide selected from at least one of Ni, Ti, Ta, Hf, Zr, V, Zn, Nb, W, and Co. Memory element.   The nonvolatile memory element according to claim 1, wherein the variable resistance layer is a metal oxide containing Hf and Al.   2. The nonvolatile memory element according to claim 1, wherein the two different resistance states are a reset state in which the low resistance changes to a high resistance and a set state in which the high resistance changes to a low resistance.   The nonvolatile memory element according to claim 1, wherein the nonvolatile memory element is a resistance change type memory.   The nonvolatile memory element according to claim 6, wherein the resistance change type memory is a ReRAM. A first electrode;
A second electrode;
A method for manufacturing a nonvolatile memory element, comprising: a variable resistance layer having a resistance value that changes between two different resistance states sandwiched between the first electrode and the second electrode,
At least one of the first electrode and the second electrode is an electrode including a metal nitride layer containing at least Ti and N;
Wherein at least the contact with the variable resistance layer portion of the Ti and N in the molar ratio of the metal nitride layer (N / Ti ratio) is not less 1.1 5 or more, and is a film density 4.7 g / cc or more, and A method for manufacturing a nonvolatile memory element, comprising a step of forming a metal nitride layer having a crystal orientation X in a range of 1.2 <X. A first electrode;
A second electrode;
A variable resistance layer sandwiched between the first electrode and the second electrode, the resistance value of which varies between two different resistance states, and the first electrode and the second electrode are A method for manufacturing a nonvolatile memory element that is an electrode including a metal nitride layer containing at least Ti and N,
Forming a metal nitride layer having a molar ratio of Ti and N (N / Ti ratio) of 1.15 or more and a film density of 4.7 g / cc or more as the first electrode;
Forming an oxide containing at least one of Ni, Ti, Ta, Hf, Zr, V, Zn, Nb, W or Co as the variable resistance layer;
Forming a metal nitride layer having a molar ratio of Ti and N (N / Ti ratio) of 1.15 or more and a film density of 4.7 g / cc or more as the second electrode; A method for manufacturing a nonvolatile memory element, comprising:   The crystal orientation X of the metal nitride layer of the first electrode is in the range of 1.2 <X, and the crystal orientation X of the metal nitride layer of the second electrode is in the range of 1.2 <X. The method for manufacturing a nonvolatile memory element according to claim 9. A first electrode;
A second electrode;
A variable resistance layer sandwiched between the first electrode and the second electrode, the resistance value of which varies between two different resistance states, and the first electrode and the second electrode are A method for manufacturing a nonvolatile memory element that is an electrode including a metal nitride layer containing at least Ti and N,
Forming a metal nitride layer having a molar ratio of Ti and N (N / Ti ratio) of 1.15 or more and a film density of 4.7 g / cc or more as the first electrode;
Forming a metal film made of at least one of Ni, Ti, Ta, Hf, Zr, V, Zn, Nb, W or Co;
Forming a variable resistance layer made of a metal oxide by heat treatment of the metal film in an oxygen atmosphere of 300 ° C. or more and 600 ° C. or less;
Forming a metal nitride layer having a molar ratio of Ti and N (N / Ti ratio) of 1.15 or more and a film density of 4.7 g / cc or more as the second electrode; A method for manufacturing a nonvolatile memory device, comprising:   The crystal orientation X of the metal nitride layer of the first electrode is in the range of 1.2 <X, and the crystal orientation X of the metal nitride layer of the second electrode is in the range of 1.2 <X. The method of manufacturing a nonvolatile memory device according to claim 11, wherein: A first electrode;
A second electrode;
A variable resistance layer sandwiched between the first electrode and the second electrode, the resistance value of which varies between two different resistance states, and the first electrode and the second electrode are A method for manufacturing a nonvolatile memory element that is an electrode including a metal nitride layer containing at least Ti and N,
Forming a metal nitride layer having a molar ratio of Ti and N (N / Ti ratio) of 1.15 or more and a film density of 4.7 g / cc or more as the first electrode;
Forming a metal film containing Hf and Al;
Forming a variable resistance layer made of a metal oxide by heat treatment of the metal film in an oxygen atmosphere of 300 ° C. or more and 600 ° C. or less;
Forming a metal nitride layer having a molar ratio of Ti and N (N / Ti ratio) of 1.15 or more and a film density of 4.7 g / cc or more as the second electrode; A method for manufacturing a nonvolatile memory element, comprising:   The crystal orientation X of the metal nitride layer of the first electrode is in the range of 1.2 <X, and the crystal orientation X of the metal nitride layer of the second electrode is in the range of 1.2 <X. The method for manufacturing a nonvolatile memory element according to claim 13, wherein the method is provided. Forming the metal nitride layer comprises:
In a vacuum vessel, a process of magnetron sputtering a Ti target in a mixed atmosphere of a reactive gas composed of nitrogen and an inert gas, and forming a metal nitride layer at least in a region in contact with the variable resistance layer, The molar ratio of Ti and N (N / Ti ratio) of the nitride layer is 1.15 or more, the film density is 4.7 g / cc or more, and the crystal orientation X is in the range of 1.2 <X. The method for manufacturing a nonvolatile memory element according to claim 8, wherein a mixing ratio of the reactive gas and the inert gas is set so as to satisfy the above.   9. The method of manufacturing a nonvolatile memory element according to claim 8, wherein the two different resistance states are a reset state in which a low resistance is changed to a high resistance and a set state in which the resistance is changed from a high resistance to a low resistance.   The method of manufacturing a nonvolatile memory element according to claim 8, wherein the nonvolatile memory element is a resistance change type memory.   The method of manufacturing a nonvolatile memory element according to claim 17, wherein the resistance change type memory is a ReRAM.

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